What causes crazing?

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Crazing is most likely caused by the heating and cooling of the Plexiglas caused by the changes in the temperature inside the aircraft. The heat build-up inside the cabin is like that inside a greenhouse. Temperatures can exceed 200 degrees F. The heat has no where to go and the Plexiglas windows heat up. Plexiglas starts out as a flat sheet and is shaped with heat. When it gets hot, it wants to return to its original flat shape. Then it cools when the sun goes down. This constant stress on the curved areas of the windshield causes what most people think of as crazing. All you have to do is look at an older windshield of an unprotected aircraft and you will notice crazing at the curved portions of the windshield. If you keep the cabin cool, the outside air movement against the Plexiglas will keep it cool and you will eliminate the stress caused by the expansion and contraction of the Plexiglas caused by extreme temperature fluctuations. Why are the shields made from aluminum with a ...
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